1. Field of the Invention
The present invention relates to an electronic apparatus for use with a transmitting and receiving unit for mobile phones.
2. Description of the Related Art
FIG. 5 is a perspective view of a conventional electronic apparatus and FIG. 6 is a cross-sectional view of the conventional electronic apparatus.
A conventional electronic apparatus such as a transmitting and receiving unit for mobile phones has a rectangular-shaped framework 21 formed by bending a metal sheet. This framework 21 is formed of four side-walls 21a having two open ends 21b, 21c opened upward and downward, respectively.
In the outer peripheral portions of the side-walls 21a, a plurality of protruded portions 21d are formed adjacent to the open ends 21b, 21c.
Inside the framework 21 appropriately attached is a flat plate-shaped printed board 22, on which a power amplifier 23 and other electronic components (not shown) are disposed to form an electric circuit by electronic printed-wiring (not shown).
Metal sheet covers 24, 25 have a plurality of tabs 24a, 25a formed by bending the outer peripheral portions thereof and holes 24b, 25b formed in the tabs 24a, 25a, respectively.
In the cover 24, which is one of the covers, a tongue-shaped portion 24c is also disposed by being downwardly cut and hung from the top wall.
The covers 24, 25 are fixed to the framework 21 by snap-fitting the holes 24b, 25b of the tabs 24a, 25a in mating with protrusions 21d formed in the framework 21, covering the top and bottom open ends 21b, 21c, respectively. As shown in FIGS. 5 and 6, the tongue-shaped portion 24c disposed in the top cover 24 is held in contact with the top surface of the power amplifier 23 disposed on the printed board 22.
In this electronic apparatus, since the power amplifier 23 generates heat, its performance may be deteriorated. When the temperature increases to the utmost, the power amplifier 23 results in failure.
When the temperature of portions adjacent to the amplifier 23 of a case of a mobile phone, etc. containing the electronic apparatus increases, a person who picks up the case has an uncomfortable feeling.
Therefore, the structure of the apparatus is formed such that the heat generated by the power amplifier 23 is conducted from the tongue-shaped portion 24c to the cover 24 which is integral therewith and further conducted to ambient air from the entire cover 24 to disperse the heat locally generated.
In the conventional electronic apparatus described above, the heat generated by the power amplifier 23 is conducted to ambient air through the tongue-shaped portion 24c extended from the cover 24. However, since the conducting path is limited to the tongue-shaped portion 24c, heat dissipation is insufficient.
When the heat dissipation is insufficient, since a heating value of the power amplifier 23 surpasses the extent of heat release to increase the temperature of the power amplifier 23, not only can the deterioration in performance of the power amplifier 23 not be prevented but also the power amplifier 23 itself might fail.